EP1281879B1 - Controlled deflection roller - Google Patents

Description

The invention relates to a pressing device for chafing a web of material, in particular paper or board web, with a gap formed between a deflection and a Begenfläche, wherein the deflection set roller a rotating roll shell, a roll shell axially passing through rotatable yoke and the yoke, on the inside of the Roller shell comprises a supporting force exerting hydrostatic support elements, each formed by a pressure fluid-actuated cylinder / piston unit and can be acted upon via a pressure chamber, and the hydrostatic pockets of the hydrostatic support elements via at least one throttle or capillary with pressurized fluid ver-provides. Such a pressing device is described, for example, in WO 98/17862 A and in EP-B-0 328 503.

In deflection adjustment rolls or deflection rolls, support sources or support elements are used, which are pressurized by a supply line with oil pressure. By this oil pressure, the respective support source is pressed against the rotating roll shell. Since the piston area of the support source is smaller than the hydrostatic pocket surface facing the roll shell, a lower pocket oil pressure is established. The pressure difference between piston pressure and pocket pressure determines the volume flow which flows through the capillaries connected between the pocket surface and the piston surface. Thus, the respective volume flow adjusts to a support source in dependence on the piston pressure.

For individual profile correction, i. in particular for the correction of certain property transverse profiles, the web passing through the nip, in particular paper or board web, the support sources are individually subjected to an oil pressure. The height of the oil pressures is regulated via an online profile thickness measurement of the material web.

Depending on the required profile corrections, there may be large differences between the oil pressures of the various support sources (e.g., from 3.5 to 90 bar from source to source). This leads, as already indicated, to volume flow differences at the support sources. Between the rotating roll shell and the support sources created by the oil shear in dependence on the shell speed and the oil gap height, which is again dependent on the flow, the oil temperature and the pocket pressure, friction. As a result of the large pressure differences thus results from a support source to another a different high friction, which affects the temperature differences on the roll shell. These temperature differences have an effect on the shape of the roll shell and thus bring with it a feedback effect influencing the generated line load profile of the deflection set roll.

Since setting a lower flow rate at a pressure relief at a support source, results in a higher temperature at this support source despite a lower amount of friction power than at higher pressures. However, a higher temperature leads to an expansion of the roll mantle, which has an effect in increasing the line load in the nip. The temperature development thus has an opposite effect to the desired pressure relief and is therefore undesirable. In some cases, this can even lead to instability in the control behavior.

Usually, the temperature development at the support sources is limited by a separate Kühlölström, which is passed into the interior of the roller. For this purpose, a volume flow of low temperature, the amount of which is regulated by the return temperature of the roller, is distributed via nozzles in the interior of the roller. So far, with such a distribution, each support source is supplied with the same amount of cooling oil. As a result of the aforementioned volume flow differences, but now set in spite of the amount of cooling oil supplied different temperatures at the support sources. This fact is substantiated by the following calculation example:

In the present calculation example is a bending compensating roll of a calender, the production speed is 1540 m / min. The surface temperature of the roller is in this case equal to the return temperature, so that no heat flow flows through the jacket.

The technical data relevant for the calculation are as follows: Outer diameter: 1016 mm Inner Diameter: 780 mm Support source size: 70 mm piston diameter Oil viscosity: ISO VG 68 (mineral oil) Inlet temperature: 40 ° C for all streams (source of support and cooling oil)

In the calculation, the temperature development and the friction power of a support source were investigated for a minimum (3.5 bar) and a maximum (90 bar) possible piston pressure as a function of the cooling flow.

FIG. 1 shows a diagram in which, for the minimum and maximum piston pressures of 3.5 bar and 90 bar, respectively, the oil temperature resulting from a support source is higher than the side flow, i.e. the pressure of the oil. Cooling flow, is shown. The temperature is given in ° C and the secondary flow in l / min. The oil temperature shown was determined directly in the outlet in the direction of the jacket behind the support source.

In the inlet of the support source oil with a mixing temperature, which results from the injection of the cooling oil inside the roll, with the roll shell entrained under the support source.

With reference to FIG. 1 it can be seen that the oil temperatures at a piston pressure of 3.5 bar are significantly higher for all investigated cooling oil flows than at a piston pressure of 90 bar.

The self-adjusting mixing temperature inside the roll corresponds approximately to the local return temperature. Figure 2 shows a diagram in which in each case the calculated return temperature over the cooling flow (secondary flow) is plotted for the two different piston pressures. It should be noted that in the calculation, only one support source was examined, ie a mixing of the oil from several sources of support with different oil pressures and thus different temperatures is disregarded.

The adjusting local return temperatures show an increasing temperature difference between a high-load and a low-loaded support source with decreasing cooling oil flows. However, such a temperature difference has a significant effect on the shape of the rotating roll shell.

In the pressing device described in WO 98/17862 A according to the preamble of claim 1, the deflection set roller is designed as a self-adjusting roller, on the support elements on the one hand during normal operation, the line load distribution adjustable and on the other hand, the gap by a corresponding displacement of the entire jacket relative to the yoke can be opened and closed. The hydrostatic pockets of the support elements during the opening and closing of the gap with a constant volume flow or constant pressure are applied. During normal operation, a temperature control takes place via the volume flow or pressure acting on the hydrostatic pockets as the respective manipulated variable.

In addition, press devices are also already known in which during the setting of a respective line load distribution, the hydrostatic pockets of the support elements of the respective deflection adjusting roller are subjected to a constant volume flow of pressurized fluid (cf., for example, US-A-4,955,120, US-A-4,856 157 and US-A-5,189,776).

In a pressing device known from US Pat. No. 4,776,069, the hydrostatic pockets of a respective support element of the respective deflection adjustment roller are supplied with pressurized fluid via the pressure chamber of the respective support element, while on the other hand they are connected to auxiliary chambers via throttle-free passages in order to ensure a pressure drop in one respective hydrostatic bag as a result of tilting of the respective support member to generate a Gegenkippmoment and thereby to keep the pressure in the respective hydrostatic bag constant.

The aim of the invention is to provide an improved pressing device of the type mentioned, in which the aforementioned problems are eliminated.

This object is achieved according to the invention in that a respective line load distribution over the piston pressure of the support elements is adjusted by a control or regulating device while the hydrostatic pockets of the hydrostatic support elements are each acted upon by at least one pre-throttle with a constant fluid pressure.

Due to this design, the temperature effect described above is reversed. Thus, smaller fluid gap heights now appear at a support element subjected to higher pressures, while larger fluid gap heights result at a support element subjected to lower pressures. With increasingly higher pressures and a correspondingly greater load of a respective support element thus correspondingly increases the friction. With increasingly smaller pressures and a correspondingly smaller load of a respective support element, the friction power is correspondingly lower. As a result, this leads at higher pressures and a correspondingly higher load of a respective support member to a correspondingly higher mixing temperature in Walzeninnem and vice versa.

But now also a reversal of the above-described, the line load distribution affecting temperature effect is effected. So now at the points where a high pressure is desired, the corresponding effect supported by the thermally induced roll expansion. At the points where a desired pressure relief is predetermined, for example via a corresponding control, a thermally induced relief results due to the roll shape. The occurring temperature effect thus supports in each case the otherwise provided for control or regulation.

In this case, the thermally assisted effect has an increased effect on the line load, since the volume flow at a respective hydrostatic bag supplied pressure fluid decreases with increasing pressure in the pressure chamber and correspondingly with increasing load of the respective support element, as applied to a high piston pressure supporting element correspondingly a higher pocket pressure adjusts, whereby the pressure difference at the choke becomes smaller. Accordingly, the volume flow at the respective hydrostatic pocket supplied pressurized fluid is lower. In contrast, resulting in smaller piston pressures and correspondingly smaller pocket pressures correspondingly larger pressure differences at the respective Vordrossel, so that correspondingly larger volume flows.

The respective pre-throttle can in particular be provided again inside the relevant support element.

Conveniently, the Vordrossel is connected at its end remote from the hydrostatic pocket to a separate from the pressure chamber, the fluid pressure constant leading channel. In this case, a respective channel may for example also be associated with a plurality of preschools.

If the respective support element has a plurality of hydrostatic pockets, then preferably each of these hydrostatic pockets is subjected to a constant fluid pressure via at least one pre-throttle.

An expedient practical embodiment of the deflection adjusting roll according to the invention is characterized in that a plurality of at least one row in the direction of the roll axis arranged behind the yoke support members are provided and that the hydrostatic pockets of all supporting elements are acted upon in each case via at least one Vorordel with a constant fluid pressure.

The respective hydrostatic pockets are preferably supplied with pressurized oil. A respective pre-throttle can thus be subjected in particular to a constant oil pressure.

Figur 1

ein Diagramm, in dem für zwei verschiedene Kolbendrücke jeweils die sich nach einer Stützquelle ergebende Öltemperatur über dem Kühlölstrom (Nebenstrom) dargestellt ist,

Figur 2

ein Diagram, in dem für zwei verschiedene Kolbendrükke jeweils die berechnete Rücklauftemperatur über dem Kühlölstrom (Nebenstrom) dargestellt ist,

Figur 3

eine Lediglich der Erläuterung der Problematik dienende schematische geschnittene Teildarstellung einer Durchbiegungseinstellwalze und

Figur 4

eine schematische geschnittene Teildarstellung einer beispielhaften Ausführungsform einer erfindungsgemäßen Durchbiegungseinstellwalze.

The invention is explained in more detail below with reference to embodiments with reference to the drawing; in this show:

FIG. 1

a diagram in which for two different piston pressures in each case the oil temperature resulting from a support source is shown above the cooling oil flow (secondary flow),

FIG. 2

a diagram in which for each two Kolbendrükke each calculated return temperature over the cooling oil flow (side stream) is shown,

FIG. 3

a merely the explanation of the problem serving schematically cut partial representation of a deflection and adjusting roll

FIG. 4

a schematic sectional partial view of an exemplary embodiment of a deflection adjustment according to the invention.

FIG. 3 shows, in a schematic sectional partial view, a deflection adjustment roller 10 which can be used to treat a material web, in particular a paper or board web, in a gap (not shown) formed with a counter surface.

The deflection adjustment roller 10 comprises a circumferential roller shell 12, a roller shell 12 axially passing through a rotationally fixed yoke 14 and a plurality of in the direction of the roller axis successively arranged on the yoke 14 hydrostatic support elements 16, of which only one can be seen in Figure 3.

The support elements 16 are each formed by a pressure fluid-actuated cylinder / piston unit which exerts a respective support force on the inside of the roller shell 12.

The support elements 16 may be individually and / or in groups controllable, resulting in corresponding, in the direction of the roll axis successive rolling zones.

The pressure chamber 18 of a respective support member 16 is acted upon via a provided in the yoke 14 channel 20 with pressurized fluid.

As can be seen from Figure 3, a respective support member 16 has a plurality of hydrostatic pockets 22, e.g. four such pockets.

In the present case, the hydrostatic pockets 22 are separated from the pressure space 18 of the respective hydrostatic support member 16 with a constant volume flow of pressurized fluid, i. especially pressure oil, supplied. For this purpose, hydraulic fluid pockets 22 are supplied with pressurized fluid via a channel 26 separated from the pressure chamber 18 and the channel 20 via throttles or capillaries 24 provided in the support element 16. This as well as the channel 20 provided in the yoke 14 channel 26 may be connected, for example via a pressure chamber 18 passing through pipe section 28 or the like with the throttles 24 and a this upstream, the various throttles 24 common space in the piston 30 of the support member 16. As can be seen from Figure 3, the piston-side end of the pipe section 28 is mounted via a pivot bearing 32 in the piston 30, so that the pipe section 28 with respect to the piston 30 is pivotable within certain limits, in particular to be able to compensate for corresponding piston movements.

If a plurality of support elements 16 arranged one behind the other at least in a row in the direction of the roll axis are provided, the hydrostatic pockets 22 of all support elements 16 are preferably supplied separately from the pressure chamber 18 of the respective hydrostatic support element 16 with a constant volume flow of pressurized fluid or pressurized oil.

In this deflection adjustment roller, the temperature effect described above is reversed. Thus, lower oil gap heights result in the case of support elements 16 subjected to a higher piston pressure and larger oil gap heights in the case of support elements 16 subjected to a lower piston pressure. As a result, the frictional power increases with increasing pressures in the pressure space 18 of each support member 16, while at lower pressures, i. decreases with a lower load of the respective support member 16. Consequently, higher piston pressures or higher loads of the support elements 16 lead to a higher mixing temperature at the support elements 16, while a respective pressure relief correspondingly brings a lower mixing temperature. The initially mentioned, the line load distribution influencing temperature effect thus acts in reverse. Thus, now at the points where a high pressure is desired, the effects caused by a corresponding pressurization of the respective support elements 16 effect supported by the thermally induced roll expansion. Accordingly, at the points where, for example, via the corresponding control or regulation, a pressure relief is desired, such a pressure relief is supported by a thermally induced relief on the roll shape.

FIG. 4 shows, in a schematic sectional partial illustration, an exemplary embodiment of a deflection adjustment roller 10 according to the invention. This deflection adjustment roller 10 can also be used, for example, for treating a material web such as, in particular, a paper or board web in a gap (not shown) formed with a counter surface. It again comprises a circulating Roll shell 12, a roll shell 12 axially passing through a rotationally fixed yoke 14 and a plurality of in the direction of the roll axis successively arranged on the yoke 14 hydrostatic support elements 16, of which only one again can be seen in Figure 4.

The support elements 16 are each again formed by a pressure fluid-operated cylinder / piston unit which exerts on the inside of the roll shell 12 a respective supporting force. In addition, the support elements can also be controlled individually and / or in groups, resulting in corresponding, in the direction of the roll axis successive rolling zones.

The pressure chamber 18 of a respective support member 16 is also acted upon again via a provided in the yoke 14 channel 20 with pressurized fluid.

Finally, the support members 16 are each again with several,. e.g. four, hydrostatic pockets 22 provided.

In the present case, the hydrostatic pockets 22 of a respective hydrostatic support element 16 are each acted upon by at least one pre-throttle 34 with a constant fluid pressure, ie in particular a constant oil pressure. For this purpose, provided in the interior of a respective support member 16 Vordrosseln 34 are connected at their remote from the respective hydrostatic bag 22 end to a separate from the pressure chamber 18, the fluid or oil constant pressure channel 36 leading. This as well as the throttles 34 provided in the piston 30 of the respective support member 16 channel 36 is connected via a provided externally on the piston 30 terminal 38 with a line 40, via the pressure fluid or pressure oil from a separate from the pressure chamber 18 and the channel 20 channel 42 in the yoke 14 to the fluid distribution to the various pre-throttles 34 serving channel 36 in the piston 30 is supplied.

Thus, a constant fluid or oil pressure is applied to the ends of the throttles 34 remote from the hydrostatic pockets 22.

For the various hydrostatic pockets 22 of a respective support member 12, a common channel 36 may be provided.

In the case of a plurality of support elements 16 arranged one behind the other at least in a row in the direction of the roll axis, preferably the hydrostatic pockets 22 of all support elements 16 are subjected to a constant fluid or oil pressure via at least one pre-throttle 34 in the described manner.

As can be seen with reference to FIG. 4, the bores for the throttles 34 have been designed as through bores for manufacturing reasons. These holes are sealed by closures 44 against the pressure chamber 18.

With such an embodiment, the supporting effect of the thermal effect on the setting of a respective distributed load distribution is enhanced. Thus, the volume flow at the hydrostatic pockets 22 of a respective support element 16 supplied pressurized fluid or pressure oil drops with increasing piston pressure, ie increasing load of the respective support element, as acted upon in one with a high piston pressure Support member 16 adjusts a correspondingly high pocket pressure and therefore results in a correspondingly smaller pressure difference at the throttles 34. With a smaller pressure difference results in a correspondingly smaller volume flow. With an increasingly smaller piston pressure and a correspondingly smaller pocket pressure of a respective support element 16, a larger pressure difference correspondingly occurs at the throttles 34, which entails a correspondingly larger volume flow.

LIST OF REFERENCE NUMBERS

10

deflection

12

roll shell

14

yoke

16

support element

18

pressure chamber

20

channel

22

Hydrostatic pocket

24

Throttle, capillary

26

channel

28

pipe section

30

piston

32

pivot bearing

34

prethrottle

36

channel

38

Connection

40

Fluid or oil line

42

channel

44

shutter

Claims (6)

1. A pressing apparatus for the treatment of a material web, in particular of a paper or cardboard web, having a gap formed between a deflection conrolled roll (10) and a mating surface, wherein the deflection controlled roll (10) comprises a rotating roll jacket (12), a rotationally fixed yoke (14) axially passing through the roll jacket (12) and hydrostatic support elements (16) which are arranged on the yoke (14), exert a supporting force on the inner side of the roll jacket (12), are formed in each case by a piston in cylinder unit actuated by pressure fluid and chargeable accordingly via a pressure space, and wherein the hydrostatic pockets (22) of the hydrostatic support element (16) are supplied with pressure fluid in each case via at least one restrictor or capillary (24),
   characterized in that
   a respective path load distribution is set by a control or regulation device via the piston pressure of the support elements (16) and, in this process, the hydrostatic pockets (22) of the hydrostatic support elements (16) are in each case charged with a constant fluid pressure via at least one pre-restrictor (34).
2. A pressing apparatus in accordance with claim 1, characterized in that the pre-restrictor (34) is provided at the interior of the relevant support element (16).
3. A pressing apparatus in accordance with claim 1 or claim 2, characterized in that the pre-restrictor (34) is connected at its end remote from the hydrostatic pocket (22) to a passage (36) separate from the pressure space (18) and conducting fluid of a constant pressure.
4. A pressing apparatus in accordance with claim 1 to claim 3, characterized in that a respective support element (16) has a plurality of hydrostatic pockets (22) and each of these hydrostatic pockets (22) is charged with a constant fluid pressure in each case via at least one pre-restrictor (34).
5. A pressing apparatus in accordance with any one of the claims 1 to 4, characterized in that a plurality of support elements (16) are provided which are arranged in series on the yoke (14) at least in one row in the direction of the roll axis; and in that the hydrostatic pockets (22) of all support elements (16) are each charged with a constant fluid pressure in each case via at least one pre-restrictor (34).
6. A pressing apparatus in accordance with any one of the claims 1 to 5, characterized in that a respective hydrostatic pocket (22) is supplied with pressure oil.

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